Conventionally, a catalyst comprising a transition metal compound and aluminoxane has been known as a highly active soluble olefin polymerization catalyst (for example, refer to Japanese Patent Applications Laid-open No. 58-19309 and No. 60-217209).
In addition, cations have been reported to be effective as an active species for a soluble olefin polymerization catalyst (for example, refer to J. Am. Chem. Soc., vol. 81, page 81 (1959); J. Am. Chem. Soc., vol. 82, page 1953 (1960), or J. Am. Chem. Soc., vol. 107, page 7219 (1986)).
As examples of the catalyst applying the separated active species to olefin polymerization, J. Am. Chem. Soc., vol. 108, page 7410 (1986), Published Japanese Translation of PCT Application No. 1-502636, Japanese Patent Application Laid-open No. 3-139504, European Patent Application Publication No. 468651, and the like can be given. In addition, as examples of a catalyst using this active species combined with an organoaluminum compound, Japanese Patent Application Laid-open No. 3-207704, International Patent Publication Pamphlet No. 92/1723, and the like can be given.
On the other hand, there are only a few reports on the use of a multiplex crosslinking (double crosslinking) metallocene complex. International Patent Publication Pamphlet No. 93/20113, Organometallics, vol. 12, page 1931 (1993), Organometallics, vol. 13, page 3868, Organometallics, vol. 17, page 5525, and J. Am. Chem. Soc., vol. 118, page 11988 have a report on this subject.
Regarding the behavior as the polymerization catalyst, Organometallics, vol. 12, page 1931 (1993) describes an example of propylene polymerization. According to the report, it is necessary to divide meso isomers of a metallocene complex from racemic isomers in order to obtain isotactic polypropylene. In addition, the resulting polypropylene has a low molecular weight.
The molecular weight of polypropylene was also small in the study on the polymerization of propylene reported by Bercaw in J. Am. Chem. Soc., vol. 118, page 11988.